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[ACKNOWLEDGED]]Hypoxia


ivo
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I to all, I know there are most important Priority to solve, but there is also the bug with oxygen supply when I turn off nothing happened instead when I get out the yellow handle of canopy its reproduce the hypoxia effects its seem an nosense, the hypoxia woul be reproduce with supply oxigen off.

 

Bye

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Hi!

 

This is not a bug at all.

 

Depending on cabin alt/press, O² supply is not necessary to provide enough partial pressure on blood cells (PaO²). As long as you have enough cabin pressure, oxygen is not needed and mixed air is alright. Once cabin press can't be maintained high enough, blood PaO² decreases ... then, breathed air has to be enriched by oxygen (O² regulator is doing its job).

 

So as long as cabin is correctly pressurized and cabin alt is not above 10000ft - 12000ft ... OXY is not needed. Pilot could even breathe without its mask on his face.

...

The yellow handle is the lock of the canopy. And one of its main role is to inflate the rubber seals. If the seals are not inflated, cabin can't be pressurized. No pressure ... with a/c altitude increasing, cabin alt increases, cabin press decreases, PaO² decrease ... pilot will eventually fall in hypoxia ... at some point, even with pure O² (out of emergency mode on regulator).

 

I will however take a look on my side. ;)

 

Regards.


Edited by Dee-Jay
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You are wrong, at 40.000 ft turn off the supply oxygen and nothing happened its is a very bug, you can get hypoxia only when you get out the yellow handle of canopy it is wrong, please investigate before speaking

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  • ED Team

Hi

 

We are aware of this,

 

Currently while the canopy is intact it is assumed the pressurised canopy has oxygen (in real life you would use up this oxygen quickly), if the oxygen is turned off and canopy is removed you will pass out.

 

I will mark this as acknowledged for now and speak to the team about it.

 

Thank you

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You are wrong, at 40.000 ft turn off the supply oxygen and nothing happened its is a very bug, you can get hypoxia only when you get out the yellow handle of canopy it is wrong, ...

Well 40.000ft is indeed quite high without O² ... but what your Cabin Alt is showing? When you say no oxygen supply, are you meaning 100% O² or just Norm? ... because you probably know that it could be a matter of time of conciseness, depending on Cabin Alt, it can be several tens of seconds up to few minutes depending on how it is implemented.

 

But if you depressurize the cockpit (either unlocking it or by turning AIRCOND to OFF or DUMP) it is a fast depressurization and CABIN ALT equals A/C Alt almost "instantaneously" ... in that case, I would indeed expect only few seconds of time of consciousness.

 

If you mean the there is now way at all of getting an hypoxia except by pulling the spider, then ok. That is not correct.

 

please investigate
Will do as soon as I can. :)

 

Regards.

 

 

EDIT: Seen BIGNEWY's post after. Good info!


Edited by Dee-Jay
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Thank for acknowledged.

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I stand: Not a bug.

 

Hi!

 

please investigate before speaking

 

So I did.

 

 

And I stand: (unless my understanding of what you've wrote is not correct), what you are describing on OP is not a bug.

 

You are wrong, at 40.000 ft turn off the supply oxygen and nothing happened its is a very bug,

 

A/C altitude do not matter. What matters is the CABIN PRESS (equivalent Cabin Altitude).

 

 

Under normal conditions, AIR SOURCE to NORM, spider locked = cabin pressurized => At 40.000ft, CABIN PRESS shows 15.000ft.

 

qFzm3mK.png

 

At FL150, you won't die. Some ppl may start suffering from hypoxia (IRL, risks starts from about FL120), but FL150 is not a dramatic altitude : refer to TUC tables here or below

 

 

Sj9I6Fu.jpg?1

 

... At FL150 more pessimistic tables gives a Time of Useful Consciousness of about half an hour.

 

IRL, I am quite used to spend hours at FL120 on an unpressurized a/c without any oxygen supply ... after four to six hours I may have a headache and heavy tiredness, but no LOC nor severe hypoxia.

 

...

Now in game: I made all kind of tests, and it is quite correctly modeled (BTW, one of the best feature in DCS IMO).

 

- At FL150, unpressurized (AIR SOURCE DUMP / SPIDER OPEN / O² REG OFF) ... I've noted no hypoxia effect at climb after 10min.

- At FL250, same condition, I start having hypoxia effect. From that point, I turn O² REG to ON ... effects disappears (means that O² REG is working)

- I set then SPDIER LOCK & AIR SOURCE to NORM ... switch off O² REG.

Cabin pressurize ... I am still FL250 but Cabin Press goes down to normal ops. Then I climb FL400.

- FL400, O² REG still on, I set it EMER (suppressed 100% supply to increase PaO²) ... I set AIR SOURCE to DUMP => Cabin Press rise rapidly at FL400 (no more delta pres I can "safely" then unlock the spider without stressing the canopy locks). Still no hypoxia effect after few minutes. And this is rather correct.

- I climp FL 570. Cabin Pess FL570, am still mask on with the O² REG on in emergency. IRL, it could not be insufficient after some time but it doesn't sound wrong to me in game. No hypoxia.

- Then I set O² REG from EMER to NOM ... still no hypoxia (this could maybe be enhanced since at this cabin altitude, even 100% O² suppressed would probably not be sufficient to reestablish proper PaO² in lungs).

- Still FL570, switching O² REG to OFF ... without few second, I rapidly get the hypoxia effects => This is fully correct. Turing immediately O² REG to ON/EMER stop the stop the progression of hypoxia effect ... but I do not fully recover.

- Setting now the spider back to locked and AIR SOURCE to NORM. Cabin Press start slowly to go down back to normal toward FL200. Now I progressively recover => this is correct.

 

 

FL570 => Cabin Press FL210

 

 

F3oMZfI.png

 

 

... theoretically, with a Cabin Pess at FL200, I could spend about 10min without O² supply.

 

- Now from FL570 I go down to FL200 and during the descent I put myself in marginal hypoxia conditions by playing depressurizing the cabin at about FL300 and playing with O² REG ... so when I reach FL200, I still have slight hypoxia effect.

 

So now at FL200, O² REG off, and full unpressurized, hypoxia effect stay there ... I am trying to see if Gs would increase the slight hypoxia effect, but no effect noticed (that could be enhanced maybe).

 

Now, still with slight hypoxia effect, I descent down to FL170-160 ... once at F150, I can fully recover without any O² supply. Well ... I imagine that my pilot is tired now and I IRL would rather go below FL120-100 to be sure to recover ... but FL150 doesn't sound bad as organism is in partial compensation.

 

 

 

So conclusions:

 

 

While there are maybe some things to enhance (combat damages?) ATM, hypoxia it really nicely implemented and quite accurate to my experience and knowledge. OP is not a bug to me and being able to stay tight at a FL150 Cabin Press without O² supply is fine for an healthy person.

 

For ppl who like to dig their knowledge about hypoxia en its effects, you can fine some more info here:

 

https://www.skybrary.aero/index.php/Hypoxia_(OGHFA_BN)

https://flightsafety.org/hf/hf_jan-feb00.pdf

 

...

 

Additionally:

 

Hi

Currently while the canopy is intact it is assumed the pressurised canopy has oxygen (in real life you would use up this oxygen quickly), if the oxygen is turned off and canopy is removed you will pass out.

 

I am not sure to understand, but the cabin is not enriched with oxygen ... not by OBOGS, nor by liquid OXY tanks.

 

O² is supplied be the mask only, so if you don't wear the mask, no O².

Cabin air comes form Air Cond system (cabin pressurisation) and is outside air mixed with hot air comng from compressor stage. At no points it is enriched in oxygen. Fortunately, otherwise cockpit would becomes highly explosive at high altitude, (remember Apollo1 accident), and would deplete O² reservoir in few minutes, and in case of OBOGS, it couldn't deliver enough O² anyway.

 

On NORM position, regulator is automatically delivering the best mix ratio between cabin air and O², 100% force the regulator to deliver 100% O² without cabin air.

And anyway, on a depressurized cabin, enriching O² in the cabin air is quickly not relevant as PaO² would not be sufficient anyway to ensure proper lungs > blood cells O² transfer.

What is (partially) reestablishing the PaO² is the 100% O² suppressed air pushed in lungs when O² REG is set on EMERG, position (which is a very unpleasant sensation but saves life.)

 

Or I've missed your point (?) ... what I mean is that currently: it is quite correctly models in the sim. I would even say, very well modeled.

 

Regards.

 

 

#s3gt_translate_tooltip_mini { display: none !important; }


Edited by Dee-Jay
I wrote "AIR COND", it is of course "AIR SOURCE".
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Ok Dj, and where is the difference between F16 and F18 about the hypoxia, if you want try also with Hornet in the same condition and let we know, bye

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Ivo, I feel some kind of aggressiveness or at least, you seems to be upset because of my posts (?). (Please see *) Maybe I wasn't really polite or diplomat when saying that your bug report was "wrong". I am sorry about that, it wasn't my intentions. I am just trying to be factual.

 

Ok Dj, and where is the difference between F16 and F18 about the hypoxia, if you want try also with Hornet in the same condition and let we know, bye

Do you mean in real life or in DCS ... ?

 

I can't tell you on F-18, I don't know that aircraft. I don't have that module and never flown on F-18. I have no idea if F-18 is correctly modeled or not ... (And to me, using a given module as reference is not a good way to prove that another is wrong).

 

I am speaking about F-16 here. But if you really wish to, I can compare it to some other a/c I know.

 

On F-16, according to the Dash-1, it looks to be more or less the same than on on all a/c I've ever flown for real in my life ... Jets (AlphaJet, M2000, MF1, Jaguar) or/and on Turbo Props (C-160, DHC-6 which is not pressurized at all). All are more or less using the same kind of systems and O² regulators are quite often exactly the same. Hypoxia risks are of course the same on all a/c ... Effects can be somehow, sometimes a bit different physiologically speaking and can change for a given person over time.

 

So I don't get your point exactly (?) ...

 

I could try to use the authority argument by telling you that I am quite concerned about hypoxia in my every-days life and that I have to pass through the hypobaric chamber once every three years. But I can't prove it and won't try anyway. So I am just trying to stick with facts, aero-medical studies, and flight manuals.

Tell me please where I am wrong (maybe I am?), but in that case, prove me I am wrong with technical arguments *rather than just using rhetoric sentences like in your last post*. That would certainly be better.

 

 

* EDIT: I may have misunderstood your tone (?)... maybe you were asking a real question (?) ... in that case, please disregard. ;)

 

...

 

 

Now ... unless ... and until you prove me wrong, if we'd like to report for a real bug, lets talk about the AIR SOURCE - OFF position:

 

On OFF position, engine bleed air valves close. All air-conditioning, cooling, and pressurizing functions shut off, including g-suit, PBG, canopy seal, fuel tank pressurization, and OBOGS ... If the AIR SOURCE knob is placed in OFF or RAM or if the ECS is inoperative, tank pressurization is not available and external fuel cannot be transferred.

 

So two things in game:

 

1 - When I set AIR SOURCE - OFF: Cabin Press do not fall down => Cockpit do not depressurize! => to my understanding and considering the above, this is wrong => "BUG" or badly implemented, or not yet fully implemented.

 

Air Source : OFF => AC altitude: 40.000ft , Cabin Press (Alt) : FL150!

 

 

ZxtHFo6.png

 

 

2 - Same conditions, with AIR SOURCE - OFF, I've never had any external tank fuel transfer issues.

Even (worse) by selection ENG FEED to OFF, no starvation, no trapped fuel issues ... no flame out. Even not by pushing negative Gs. But this is part of another issues about ENG FEED.

 

To sum-up : AIR SOURCE - NORM still pressurizing the cockpit => that is indeed a bug.

 

 

 

I let you guys opening a proper bug-tracker/report for that specific one if you which. I am not that much familiar with forum procedures yet.

 

Regards.


Edited by Dee-Jay
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From Dj :

 

ivo, I feel some kind of aggressiveness or at least, you seems to be upset because of my posts. Maybe I wasn't really polite or diplomat when saying that your bug report was "wrong". I am sorry about that, it wasn't my intentions. I am just trying to be factual.

 

absolutely not, I am interested in your explanation that denotes a good knowledge of the subject, I just want to understand how the effect of hypoxia works, from what I understood it does not depend only on the presence of oxygen but also on the presurization you link a video of a friend who tried this on both the F14 and F18

 

 

Bye and thank my friend :thumbup:

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Thanks DJ for the investigation, that sounds like normal operations for a Diluted Demand/PP Face mask and a pressurized compartment.

 

 

I own the F/A-18C so I can try your same tests, but as you mentioned other than some hypoxia tweaks (fatigue, positive pressure requirement at very high alt etc) that sounds like normal operation.

 

 

Setting the air source to OFF shouldn't cause an immediate pressurization loss, as residual pressure exists. At constant altitude there is a "slow leak" through seal/valves.. and while I'm not experienced with external tanks, it sounds like residual pressure in the tanks could keep them feeding (this could also be a source of leaking pressure - air entering the tank replacing fuel volume).

 

 

 

A good test might be to pressurize the cockpit, note the cabin altitude, then turn the source to OFF and climb say 10,000ft. ΔP shouldn't change, and cabin altitude should be somewhere around 10,000ft higher.

 

 

I'll test the F/A-18C and report back.

The F/A-18C handles basically the same way, with some minor differences. Apparently the FLOW knob controls all airflow to the mask regardless of the source. Turning FLOW to OFF on the ground after engine start (pilot dons mask) will result in hypoxia. There are no controls for 100%/EMER (apparently it's on the mask/suit?) and the only controls in the cockpit are FLOW and OBOGS ON/OFF. Dumping the cockpit at altitude results in hypoxia unless OBOGS/FLOW is turned on. With cabin pressurized (BLEED NORM or OFF), OBOGS can be turned off at any altitude with no hypoxia. BLEED OFF results in little change in differential pressure, but it's interesting that the pilot can withstand 3+ minutes at a cockpit altitude of 19,000ft with no hypoxia effect (OBOGS OFF). Seconds after turning the bleeds off TK PRES LO (tank pressure low) is displayed.

 

 

Also the manual mentions a momentary OBOGS DEGD nuisance message when turning the system ON or OFF, and that's modeled for turning the system ON. The message also displays when afterburner is selected and it's OFF while bleeds are OFF.


Edited by randomTOTEN
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absolutely not,

 

... so please accept my apologies for my own misunderstanding

 

thumbup.gif ...

 

About the video of Grim Reaper, he is continuously speaking about oxygen supply, masks ... , but never talk about cabin pressure (Cabin Altitude) ... a nice video he made, but he simply didn't talked about the most important part of the subject.

 

it does not depend only on the presence of oxygen but also on the presurization
Correct. Pressure is even more important than O² ... it is exactly the same mechanism for divers, but on the other way => need less O² with depth increasing (more pressure => more PaO2) but are using more "air" because it is "less decompressed" in lungs.

 

 

O² is one thing, but without pressure (PaO²) to ensure O² transfer from lungs alveolis to blood cells, oxygen is pointless. More PaO², less O² needed.

 

It is all about having enough pressure to to the transfer (=> EMERGENCY mode of regulator which is literally blowing/pushing air into your lungs.

I didn't talk about nitrogen, barotrauma ... etc ... but that is another story.

 

A good test might be to pressurize the cockpit, note the cabin altitude, then turn the source to OFF and climb say 10,000ft. ΔP shouldn't change, and cabin altitude should be somewhere around 10,000ft higher.

 

 

Good point.

But from an depressurized situation, (A/C FL250 and Cabin Alt FL250) I was able to re-pressurize the cabin by switching the AIR SOURCE from DUMP to OFF position. :huh: :smoke:IMHO => bug here. ;)

 

And I was able to empty both external tanks with no issues ... even without ENG FEED to NORM ... inverted, and even with negative Gs! :music_whistling:

 

 

Best regards gents.


Edited by Dee-Jay
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I was able to re-pressurize the cabin by switching the AIR SOURCE from DUMP to OFF position. :huh: :smoke:IMHO => bug here. ;)

I actually suspect we might just be finding the current limits of the simulation. Probably not fair to call that a bug either.

 

 

In the F/A-18C turning the bleed OFF results in the cockpit following the normal pressurization schedule (I.E. trapped cockpit pressure isn't modeled) I just tried another test. EDIT: Actually it pressurizes with bleed OFF just like the Viper, although it's at a slower rate!

In the F-16C like you mentioned turning the bleed OFF repressurizes the cockpit.

In the A-10C turning the bleed OFF (or AIR SUPPLY) simply outright dumps the cockpit pressure.


Edited by randomTOTEN
i have to keep replacing "cabin" with "cockpit" because fighters don't have cabins lol
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I actually suspect we might just be finding the current limits of the simulation. Probably not fair to call that a bug either.
Well ... I know that it is not a simulation (code) limitation, at least elsewhere (!) and honestly, it is no big deal once identified. Ed do other things much more complex every days. I am not worried ... it will be fixed. ;)

Cheers!


Edited by Dee-Jay
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...

 

A good test might be to pressurize the cockpit, note the cabin altitude, then turn the source to OFF and climb say 10,000ft. ΔP shouldn't change, and cabin altitude should be somewhere around 10,000ft higher.

 

 

Now I am thinking about it ... nope, this won't probably happen IRL.

When switching AIR SOURCE to OFF, canopy rubber seals deflates. IMO, considering the type of canopy, we will be closer to a rapid decompression than a slow decompression. What you say above could be valid if seals were still inflated and tight.

 

 

...


Edited by Dee-Jay
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ok but in the F-16 where is the command to pressurize the cabin.

 

bye

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Then, air source set to Off, Norm or Dump has no effects, instead set to Ram over the 30.000 feet its gets cabin pressure faillure and turn off the oxigen has hypoxia. Its works fine ?

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set AIR SOURCE to RAM, cockpit depressurize. try and let my know....I get depressurize set to RAM

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Just tried it, yes the cockpit depressurizes when AIR SOURCE is set to RAM.

 

 

Its works fine ?
It's not perfect, but it's not broken.

 

 

IMO, considering the type of canopy, we will be closer to a rapid decompression than a slow decompression.
DJ you make a great point about the canopy seal. So we wouldn't have a "slow leak" as that seal has basically failed.

But I guess that it isn't a rapid decompression. My only evidence for this is the existence of a DUMP setting in all these aircraft (Viper included). If depressurizing the seal performed the same action, what would be the point of having this switch setting (i.e. it would be redundant)?

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If depressurizing the seal performed the same action, what would be the point of having this switch setting?

 

Because it would be unsafe to "unlock" the canopy during the flight ;) ... especially if cockpit is still pressurized and ΔP not zero! ...

 

On some other aircrafts I've flown ... canopy lock and canopy seal inflating command is not the same.

 

Here is on Alpha Jet (more or less the same on Mirage and Jaguar) :

 

 

"Climat" switch is turning ECS "ON" and inflates the rubber seal ...

 

ddq3BPB.jpg

...

 

Red handle is just locking the canopy.

 

V2iFwmF.jpg


Edited by Dee-Jay
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Because it would be unsafe to "unlock" the canopy during the flight
That's true, but I was trying to suggest that you could depressurize the canopy seal by setting the AIR SOURCE switch to either OFF or RAM... no physical unlocking of the canopy required (although that too deflates the seal) and no DUMP position required.

 

 

Looking at the Hellenic AF manual, it states that both DUMP and RAM open the "cockpit pressure dump valve." DUMP keeps the air supply going, and RAM introduces ram air into the system. Air leaking past the canopy must not be enough to rapidly depressurize, thus the ability to open the valve, but pressure loss would still be substantial by my guess.

 

 

Have you guys ever depressurized the cockpit in flight? as part of training?

 

 

 

EDIT: Those controls look identical to the RAZBAM M-2000C :)


Edited by randomTOTEN
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